Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$134.47	5.259%	$141.5418	$141.54	$141.55	$141.50
Purchase #2	$133.83	12.662%	$150.7756	$150.78	$150.80	$150.80
Purchase #3	$219.83	13.727%	$250.0061	$250.01	$250.00	$250.00
Purchase #4	$70.37	6.744%	$75.1158	$75.12	$75.10	$75.10
Purchase #5	$98.39	8.174%	$106.4324	$106.43	$106.45	$106.40
Purchase #6	$240.64	8.150%	$260.2522	$260.25	$260.25	$260.30
Purchase #7	$73.82	4.598%	$77.2142	$77.21	$77.20	$77.20
7 purchase totals =	$971.35		$1,061.3381	$1,061.34	$1,061.35	$1,061.30